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News Flashes are brief overviews of current studies conducted in the Health and Fitness industry on a variety of topics. We choose those that relate to the female athlete. Enjoy reading… __________________________________________________________________
Knee Injuries Due To Brain Drain? Recently, IDEA Fitness Journal reported on a study that stated that mental fatigue can limit physical performance. Another, more recent study has linked mental fatigue with anterior cruciate ligament (ACL) injuries among athletes. The study, published in the August issue of Medicine & Science in Sports & Exercise (2009; 41 [8], 1662-73), suggested that the brain is just as important as muscle in preventing ACL injuries. The study participants included 20 female NCAA athletes who performed one-legged squats to fatigue. Immediately following, the authors then tested the athletes' reactions to various jumping and movement commands. The results determined that injury risk increased for both legs, not just the leg that was prefatigued. "Unilateral fatigue induces a fatigue crossover to the contralateral limb during single-leg standings," stated the authors. "Central fatigue thus seems to be a critical component of fatigue-induced sports landing strategies." The authors suggested that greater focus on training central control processes should be implemented for injury prevention purposes. Author Credit: Ryan Halvorson, associate editor, IDEA Fitness Journal, Source: November-December 2009 IDEA Fitness Journal, www.ideafit.com
Eating Behaviors and Girls’ Bone Loss
Adolescent girls who compete in athletic events sometimes fall victim to disordered eating, which has been linked to low bone mineral density (BMD). To explore the specific eating behaviors that lead to low BMD, researchers recently compared the attitudes and concerns of teenage girls who were endurance runners.
The study participants were 93 female competitive cross-country runners ranging in age from 13-18. The adolescents were assessed for different types of disordered eating, such as weight concern, shape concern, eating concern and dietary restraint, along with BMD history.
After adjusting for other variables, such as menstrual irregularities, the researchers found that dietary restraint was the behavior most associated with low BMD. Concerns regarding weight, shape and eating (or any combination of these three concerns) were not significantly associated with low BMD.
Reporting in the January issue of The American journal of Clinical Nutrition, the researchers concluded that “in adolescent female runners, dietary restraint may be the disordered eating behavior most associated with negative bone health effects.”
Author Credit: Diane Lofshult, senior editor of IDEA Fitness Journal, Source: July-August 2008 IDEA Fitness Journal, www.ideafit.com
Substrate Utilization and Estrogen
Differences in metabolism exist between males and females. Several studies have shown that males have greater glycolytic (carbohydrate) capacity and rely more on glycolytic pathways, whereas females rely more on oxidative phosphorylation (fat and carbohydrate) during sustained cardiovascular exercise (Braun & Horton 2001; Tarnopolsky et al. 1990). Muscle biopsy research shows that the common glycolytic enzymes (phosphofructokinase, pyruvate kinase and lactate dehydrogense) that break down carbohydrate are less active in women possibly decreasing their potential for glycolytic-pathway energy production (Tarnopolsky 2008). Thus, it is proposed that females will make greater use of the longer-lasting fat metabolism pathway during cardiovascular exercise.
Estrogen has been shown to influence the utilization of different fuels (i.e., fats, proteins and carbohydrates), especially during long endurance exercise (Tarnopolsky 2008). Females typically rely less on carbohydrate and muscle glycogen stores and more on fat oxidation during endurance exercise, even with carbohydrate-loading diets. This finding has led researchers to believe that estrogen has glycogen-sparing characteristics (Braun $ Horton 2001; Tarnopolsky 2008; Tarnopolsky et al. 1990).
Author Credit: Len Kravitz, PhD, and Brenda Critchfield, ATC, LAT, CSCS Source: June 2008 IDEA Fitness Journal, www.ideafit.com
Neuromuscular Control in Female Athletes May Help Prevent ACL Injuries
Valgus knee movement in women is considered a major contributor to the incidence of anterior cruciate ligament (ACL) injuries, according to an article published last fall in the Strength and Conditioning Journal (2006;28 [5], 44-54). The article also states that women are four to six times more likely to suffer ACL injury than and that, upon load, a 5-degree valgus angle at the knee stresses the ligament six times as much as a properly aligned knee. Such factors as ligament, quadriceps and leg dominance; joint position and range of motion; core instability; and neuromuscular fatigue are thought to affect neuromuscular control of the knee. Female athletes who commonly jump or make quick directional changes in their sport are especially vulnerable to injury.
Author Donald V. Fischer, MSPT, suggests counteracting predisposition to injury by using training methods that improve “conscious awareness of body position and body movement prior to the initiation of a motor command and the conscious awareness of the consequences of the motor command after it has been initiated.” Fischer also advises integrating exercises that focus on core strength, knee-flexion range of motion and decreased knee abduction in accordance with plyometric, balance and perturbation training.
Reprinted with permission from IDEA Health and Fitness Association, www.ideafit.com
Author Credit: Ryan Halvorson, March 2007 IDEA Fitness Journal.
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